Insect feeding deterrent activity of phytoalexin isoflavonoids

When incorporated into an agar-cellulose medium containing feeding stimulants, phytoalexin isoflavonoids from several legumes show feeding deterrent activity against larvae of the insect Costelytra zealandica and Heteronychus arator. The levels at which these compounds deter feeding are of the same order of magnitude as those at which they reduce fungal growth. The most active compound tested was phaseollin. These results suggest that phytoalexin isoflavonoids show a dual acitvity against insects and fungi.     

New pterocarpan phytoalexins from Lathyrus nissolia

In addition to 3-hydroxy-9-methoxypterocarpan (medicarpin), the fungus-inoculated phyllodes of Lathyrus nissolia produce two previously unreported isoflavonoid phytoalexins. These compounds have been identified as 3,9-dihydroxy-10- methoxypterocarpan (nissolin) and 3-hydroxy-9,10-dimethoxypterocarpan (methyl-nissolin).     

Flavonoids from Millettia pulchra

Chemical examination of Millettia pulchra yielded (?)-maackiain, (?)-pterocarpin, (?)-sophoranone and the new compounds (6S, 6aS, 11aR)-6α-methoxypterocarpin, (6S, 6aS,11aR)-6α-methoxyhomopterocarpin, (2S)5,7,4′-trihydroxy-8,3′,5′-triprenylflavanone, (2R,3R)7,4′-dihydroxy-8,3′,5′-triprenyldihydroflavanol, 5,7,2′,4′-tetrahydroxy-6,3′-diprenylisoflavone and 5,7,4′-trihydroxy-2′-methoxy-6,3′-diprenylisoflavone.     

Erybraedin C and bitucarpin A, two structurally related pterocarpans purified from Bituminaria bituminosa, induced apoptosis in human colon adenocarcinoma cell lines MMR- and p53-proficient and -deficient in a dose-, time-, and structure-dependent fashion

Pterocarpans, the second group of natural isoflavonoids, have received considerable interest on account of their medicinal properties. These drugs are employed as antitoxins, but display antifungal, antiviral and antibacterial properties as well. Erybraedin C and bitucarpin A are two new structurally related pterocarpans recently purified and characterized. Bitucarpin A differs from erybraedin C for the absence of a prenyl group in 5' position and the presence of a methoxylate hydroxyl group in 7, 4' positions. These compounds proved not to be clastogens in human lymphocytes per se but displayed anticlastogenic activity against mytomicin C and bleomycin C. Here we extended the study of their antiproliferative and apoptosis-inducing mechanism on human cell lines. Two human adenocarcinoma cell lines, LoVo and HT29, as examples of slow-growing solid tumors, proficient and deficient in mismatch repair system (MMR), p53 and Bcl-2, were used to evaluate the cytotoxicity of the drugs and their effects on the cell cycle, measured by flow cytometry. Erybraedin C similarly affects the survival of HT29 (MMR +/+, p53 -/- and Bcl-2 +/+) and LoVo (MMR -/-, p53 +/+ and Bcl-2 -/-) cells (LD(50): 1.94 and 1.73 microg/ml, respectively). By contrast, bitucarpin A exhibits a differential cytotoxicity in the cell lines (LD(50): 6.00 microg/ml, HT29, and 1.84 microg/ml, LoVo). The cell cycle distributions of the LoVo and HT29 cells treated with erybraedin C lacked a specific checkpoint arrest, whereas they underwent a characteristic sub-G(1) peak, time- and drug-concentration dependent. So that apoptotic process induced by erybraedin C in both adenocarcinoma cell lines is independent of cell cycle arrest and of phenotypic status of the cells as well. By contrast, bitucarpin A affects cell cycle progression on both cell lines, inducing a transient block in G(0)/G(1) along 24-96 h, and induces apoptosis with a cell density and treatment time dependency. Similar results were obtained with the positive control drug etoposide. The programmed cellular death on human adenocarcinoma cell lines may be efficiently activated, via a topoisomerase II poison pattern, by erybraedin C, the drug containing regio-specific hydroxyl and prenyl groups. The apoptotic effect induced by the methoxylated bitucarpin A proved to be conditioned by cell density and required higher dose (5-fold-LD(50)) and longer treatment time. The present study provides evidences that erybraedin C may act as a potent growth inhibitory compound, at low and high cell density, comparable to other clinically important antineoplastic natural drugs including etoposide, on human colon adenocarcinoma cells. Bitucarpin A proved less active because it was conditioned by cell density effect, but this finding may represent a clinical advantage against early micrometastatic diseases.     

Pterocarpans and Isoflavans from Astragalus membranaceus (Fisch.) Bunge

A new pterocarpan, (6aR, llaR)-3, 9-dimethoxy-l0-hydroxypterocarpan with four known compounds, (6aR,11aR)-3,9,10-tri-methoxypterocarpan,9,l0-di-methoxypterocarpan-3-O-β-D-glucopyranoside, (3R)-2'-hydroxy-7, 3', 4'-trimethoxy-isoflavan, 2'-hydroxy-3', 4'- dimethoxyisoflavan-7-O-β-D-glucopyranoside, were isolated from ethanolic extract of the root of Astragalus membranaceus (Fisch.) Bunge. Their structures were elucidated by means of spectral analysis and chemical conversions.     

6a-hydroxypterocarpans from red clover

Pisatin and homopisatin have been identified as antifungal compounds in red clover infected with either Botrytis cinerea, a non-pathogen, or Sclerotinia trifoliorum a clover pathogen. In addition 6a- hydroxymaackiain and 6a-hydroxymedicarpin have been detected. In vitro experiments have established that Sclerotinia can convert both maackiain and medicarpin to their respective 6a-hydroxylated products.     

Vestitol and vesticarpan,isoflavonoids from Machaerium vestitum

The wood of Machaerium vestitum contains the previously described O-acetyloleanolic aldehyde, formononetin, (+)-medicarpin, and (?)-mucronulatol, besides (+)-vestitol [(3S)-7,2′-dihydroxy-4-methoxyisoflavan] and (+)-vesticarpan [(6aS,11aS)-3,10-dihydroxy-9-methoxypterocarpan]. The constitutions of vestitol and vesticarpan were deduced by spectra and confirmed by syntheses.     

Pterocarpans from Swartzia laevicarpa

An ethanol extract of the trunkwood from Swartzia laevicarpa (Leguminosae) gave four (6aR,11aR)-8-hydroxy-3,9-dimethoxypterocarpans differentiated by additional 2-hydroxy, 2-hydroxy-10-methoxy, 4,10-dimethoxy and 2-hydroxy-4,10-dimethoxy substitution; besides two 8-hydroxy-6-methoxy-3-methylisocoumarins differentiated by 5-chloro and 7-chloro substitution; 5-hydroxy-7,8-dimethoxy-2-methylchromone and the known 8-hydroxy-5-methyl-3,4-dihydroxyisocoumarin.     

Arbuscular mycorrhizal fungi alter the content and composition of secondary metabolites in Bituminaria bituminosa L.

• Secondary metabolites may be affected by arbuscular mycorrhizal fungi (AMF), which are beneficial symbionts associated with the roots of most plant species. Bituminaria bituminosa (L.) C.H.Stirt is known as a source of several phytochemicals and therefore used in folk medicine as a vulnerary, cicatrising, disinfectant agent. Characteristic metabolites found in B. bituminosa are furanocoumarins and pterocarpans, which are used in cosmetics and as chemotherapeutic agents. Here we address the question whether AMF inoculation might affect positively the synthesis of these phytochemicals.
• B. bituminosa plants were inoculated with different AMF and several metabolites were assessed during full vegetative stage and flowering phase. Pigments (chlorophylls and carotenoids), polyphenols and flavonoids were spectrophotometrically determined; specific isoflavones (genistein), furanocoumarins (psoralene and angelicin), pterocarpans (bitucarpin A and erybraedin C) and plicatin B were assessed with HPLC; leaf volatile organic compounds were analysed using SPME and identified by GC‐MS.
• During the vegetative stage, the inoculated plants had a high amount of furanocoumarins (angelicin and psoralen) and pterocarpans (erybraedin C and bitucarpin A). The analysis of volatile organic compounds of inoculated plants showed different chemical composition compared with non‐mycorrhizal plants.
• Given the important potential role played by furanocoumarins and pterocarpans in the pharmaceutical industry, AMF inoculation of B. bituminosa plants may represent a suitable biotechnological tool to obtain higher amounts of such metabolites for pharmaceutical and medicinal purposes.

     

Tephrocarpin,a pterocarpan phytoalexin from Tephrosia bidwilli and a structure proposal for acanthocarpan

The isoflavonoids (-)-6aR; 11aR-maackiain, (-)-6aS; 11aS-pisatin and (-)-6aR; 11aR-4-methoxy- maackiain have been isolated as p